Motorcycle including brake-by-wire system with flexibly supported pressure-generating unit

ABSTRACT

In a brake system for a motorcycle in which the operation of a pressure-regulating unit interposed between fluid pressure-generating unit and a wheel brake so as to regulate an output fluid pressure of the fluid pressure-generating unit and to apply the regulated fluid pressure to the wheel brake is controlled by a control unit on the basis of a value detected by operating amount detector for detecting an operating amount of a brake operating element, to arrange the fluid pressure-generating unit in a location which is close to the pressure control unit disposed on the rear side of an engine body and in which an installation space is easy to secure. The fluid pressure-generating unit, laid out in plan view between a left-right pair of seat rails which constitute a part of a body frame and which support a riders&#39; seat, is supported by the seat rails.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims priority under 35 USC 119 based on Japanesepatent application No. 2008-091950, filed on Mar. 31, 2008. The entiresubject matter of this priority document, including specification claimsand drawings, is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a motorcycle including an operatingamount detector for detecting an operating amount of a brake operatingelement, fluid pressure-generating unit capable of generating a fluidpressure independently of an operation of the brake operating element, apressure-regulating unit interposed between the fluidpressure-generating unit and a wheel brake so as to regulate an outputfluid pressure of the fluid pressure-generating unit and to apply theregulated fluid pressure to the wheel brake, and a control unit forcontrolling the operation of the pressure-regulating unit on the basisof a value detected by the operating amount detector, thepressure-regulating unit being arranged on the rear side of an enginebody mounted on a body frame.

2. Description of the Background Art

A configuration in which fluid pressure-generating unit and apressure-regulating unit are mounted to a body frame on the rear side ofan engine mounted on a motorcycle has been known, as described in theJapanese Patent Publication Nos. Sho 63-17662 and Hei 7-88158.

Meanwhile, in the configuration as disclosed in the Japanese PatentPublication Nos. Sho 63-17662 and Hei 7-88158, the fluidpressure-generating unit and the pressure-regulating unit are unitized.However, the fluid pressure-generating unit and the pressure-regulatingunit may be arranged separately. In that case, it is desirable that thefluid pressure-generating unit be disposed at a position which iscomparatively close to the pressure-regulating unit and at which aninstallation space is easy to secure.

The present invention has been made in consideration of theabove-mentioned circumstances. Accordingly, it is an object of thepresent invention to provide a motorcycle in which fluidpressure-generating unit is arranged in a location which is close to apressure-regulating unit disposed on the rear side of an engine body andin which an installation space is easy to secure.

SUMMARY OF THE INVENTION

In order to achieve the above objects, In order to attain the aboveobject, the invention according to claim 1 resides in a motorcycleincluding operating amount detector for detecting an operating amount ofa brake operating element, fluid pressure-generating unit capable ofgenerating a fluid pressure independently from an operation of the brakeoperating element, a pressure-regulating unit interposed between thefluid pressure-generating unit and a wheel brake so as to regulate anoutput fluid pressure of the fluid pressure-generating unit and to applythe regulated fluid pressure to the wheel brake, and a control unit forcontrolling the operation of the pressure-regulating unit on the basisof a value detected by the operating amount detector, thepressure-regulating unit being disposed on the rear side of an enginebody mounted on a body frame, characterized in that the fluidpressure-generating unit, laid out in plan view between a left-rightpair of seat rails which constitute a part of the body frame and whichsupport a riders' seat, is supported by the seat rails.

The invention according to claim 2 is characterized in that, in additionto the configuration of the invention according to claim 1, the fluidpressure-generating unit is floatingly supported, through an elasticmember, by a first support member which is attached to one of both theseat rails and by a crossmember which connects both the seat rails toeach other.

The invention according to claim 3 is characterized in that, in additionto the configuration of the invention according to claim 2, a secondsupport member is firmly attached to the crossmember, and an attachingmember fixed to the fluid pressure-generating unit is supported by thesecond support member through an elastic member.

The invention according to claim 4 is characterized in that, in additionto the configuration of the invention according to any of claims 1 to 3,a shock absorber is provided between a swing arm which is swingablyborne on the body frame while rotatably bearing a rear wheel and a linkmember which constitutes a part of a link mechanism provided between theswing arm and the body frame, and a sub-tank disposed on the rear sideof the fluid pressure-generating unit so as to condition the dampingforce of the shock absorber is supported by the seat rail.

The invention according to claim 5 is characterized in that, in additionto the configuration of the invention according to claim 4, a sub-tanksupport member for supporting the sub-tank is fixed to the seat rail byco-fastening thereof together with a pillion step.

Incidentally, the brake pedal 16 in the embodiment below corresponds tothe brake operating element in the present invention, the rear fluidpressure-generating unit 17R in the embodiment corresponds to the fluidpressure-generating unit in the invention, the rear pressure-regulatingunit 18R in the embodiment corresponds to the pressure-regulating unitin the invention, the first pressure sensor 34 in the embodimentcorresponds to the operating amount detector in the invention, therubber bushing 156 in the embodiment corresponds to the elastic memberin the invention, and the rear wheel brake BR in the embodimentcorresponds to the wheel brake in the invention.

EFFECTS OF THE INVENTION

According to the invention of claim 1, the fluid pressure-generatingunit is supported by the left-right pair of seat rails for supportingthe riders' seat, and is laid out between both the seat rails in planview. Therefore, the fluid pressure-generating unit can be arranged in alocation which is close to the pressure-regulating unit disposed on therear side of the engine body and in which a space necessary forinstalling the fluid pressure-generating unit is easy to secure.

In addition, according to the invention of claim 2 or 3, the fluidpressure-generating unit is floatingly supported by the first supportmember which is attached to one of both the seat rails and by thecrossmember which connects both the seat rails to each other. Therefore,vibrations on the body frame side can be restrained from reaching thefluid pressure-generating unit.

According to the invention of claim 4, the fluid pressure-generatingunit is arranged between the sub-tank and the engine body, whereby thefluid pressure-generating unit can be protected from external forces.

Furthermore, according to the invention of claim 5, the sub-tank supportmember is fixed to the seat rail by co-fastening thereof together withthe pillion step, and, therefore, the number of component parts can bereduced.

For a more complete understanding of the present invention, the readeris referred to the following detailed description section, which shouldbe read in conjunction with the accompanying drawings. Throughout thefollowing detailed description and in the drawings, like numbers referto like parts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the configuration of a brake system for amotorcycle.

FIG. 2 is a left side view of the motorcycle.

FIG. 3 is an exploded perspective view of a support structure for afront pressure unit.

FIG. 4 is a perspective view showing the condition where the frontpressure-regulating unit is supported by support unit.

FIG. 5 is a side view showing the condition where the frontpressure-regulating unit is supported on a body frame.

FIG. 6 is a plan view taken along arrow 6 of FIG. 5.

FIG. 7 is a sectional view taken along line 7-7 of FIG. 6.

FIG. 8 is a partly cut-away front view, as viewed along line 8-8 of FIG.2, of the body frame, an engine body and front fluid pressure-generatingunit.

FIG. 9 is a sectional view taken along line 9-9 of FIG. 8.

FIG. 10 is a sectional view taken along line 10-10 of FIG. 8.

FIG. 11 is a sectional view taken along line 11-11 of FIG. 9.

FIG. 12 is an enlarged sectional view taken along line 12-12 of FIG. 9.

FIG. 13 is an enlarged sectional view taken along line 13-13 of FIG. 9.

FIG. 14 is a view from the rear side of a rear pressure-regulating unitand the body frame.

FIG. 15 is a sectional view taken along line 15-15 of FIG. 14.

FIG. 16 is a sectional view taken along line 16-16 of FIG. 14.

FIG. 17 is an enlarged view of that portion of FIG. 2 which shows therear fluid pressure-generating unit and the surroundings thereof.

FIG. 18 is a view taken along arrow 18 of FIG. 17.

FIG. 19 is a perspective view taken along arrow 19 of FIG. 17.

FIG. 20 is a perspective view taken along arrow 20 of FIG. 17.

FIG. 21 is a sectional view taken along line 21-21 of FIG. 18.

FIG. 22 is an enlarged view of that portion of FIG. 2 which shows acontrol unit and the vicinity thereof.

FIG. 23 is a view, corresponding to FIG. 22, showing the condition wherea front cowl is removed.

FIG. 24 is a view showing the condition where the control unit isremoved from the condition shown in FIG. 23.

FIG. 25 is a sectional view taken along line 25-25 of FIG. 22.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

An embodiment of the present invention will now be described, withreference to the drawings. Throughout this description, relative termslike “upper”, “lower”, “above”, “below”, “front”, “back”, and the likeare used in reference to a vantage point of an operator of the vehicle,seated on the driver's seat and facing forward. It should be understoodthat these terms are used for purposes of illustration, and are notintended to limit the invention. Further, it should be noted that wherea reference number is followed herein by multiple dots such as . . . ,that is a short way of indicating that more than one of that referencedcomponent is present in the assembled structure.

Now, a mode of carrying out the present invention will be describedbelow, based on one embodiment of the invention shown in the attacheddrawings.

FIGS. 1 to 25 illustrate one embodiment of the present invention, inwhich FIG. 1 is a diagram showing the configuration of a brake systemfor a motorcycle; FIG. 2 is a left side view of the motorcycle; FIG. 3is an explodes perspective view of a support structure for a frontpressure-regulating unit; FIG. 4 is a perspective view showing thecondition where the front pressure-regulating unit is supported by thesupport unit; FIG. 5 is a side view showing the condition of support ofthe front pressure-regulating unit on a body frame; FIG. 6 is a planview taken along arrow 6 of FIG. 5; FIG. 7 is a sectional view takenalong line 7-7 of FIG. 6; FIG. 8 is a partly cut-away front view, asviewed along line 8-8 of FIG. 2, of the body frame, an engine body andfront fluid pressure-generating unit; FIG. 9 is a sectional view takenalong line 9-9 of FIG. 8; FIG. 10 is a sectional view taken along line10-10 of FIG. 8; FIG. 11 is a sectional view taken along line 11-11 ofFIG. 9; FIG. 12 is an enlarged sectional view taken along line 12-12 ofFIG. 9; FIG. 13 is an enlarged sectional view taken along line 13-13 ofFIG. 9; FIG. 14 is a view from the rear side of a rearpressure-regulating unit and the body frame; FIG. 15 is a sectional viewtaken along line 15-15 of FIG. 14; FIG. 16 is a sectional view takenalong line 16-16 of FIG. 14; FIG. 17 is an enlarged view of that portionof FIG. 2 which shows the rear fluid pressure-generating unit and thesurroundings thereof; FIG. 18 is a view taken along arrow 18 of FIG. 17;FIG. 19 is a perspective view taken along arrow 19 of FIG. 17; FIG. 20is a perspective view taken along arrow 20 of FIG. 17; FIG. 21 is asectional view taken along line 21-21 of FIG. 18; FIG. 22 is an enlargedview of that portion of FIG. 2 which shows a control unit and thevicinity thereof; FIG. 23 is a view, corresponding to FIG. 22, showingthe condition where a front cowl is removed; FIG. 24 is a view showingthe condition where the control unit is removed from the condition shownin FIG. 23; and FIG. 25 is a sectional view taken along line 25-25 ofFIG. 22.

First, in FIG. 1, a front wheel brake BF provided in a motorcycle isprovided with a front pressure-regulating unit 18F by which a fluidpressure outputted from a front master cylinder MF according to anoperation of a brake lever 15 serving as a brake operating element canbe exerted and by which a fluid pressure outputted from front fluidpressure-generating unit 17F can also be exerted. The frontpressure-regulating unit 18F is interposed between the front mastercylinder MF and the front fluid pressure-generating unit 17F, and thefront wheel brake BF. In addition, the rear wheel brake BR is providedwith rear pressure-regulating unit 17R by which a fluid pressureoutputted from a rear master cylinder MR according to an operation of abrake pedal 16 serving as a brake operating element can be exerted andby which a fluid pressure outputted from rear fluid pressure-generatingunit 17R can also be exerted. The rear pressure-regulating unit 18R isinterposed between the rear master cylinder MR and the rear fluidpressure-generating unit 17R, and the rear wheel brake BR.

The front fluid pressure-generating unit 17F, which generates a fluidpressure by operation of an electric motor 19, includes: the electricmotor 19, a piston 22 slidably fitted in a cylinder body 20 whileforming a fluid pressure chamber 21 between itself and the cylinder body20; a return spring 23 disposed between the cylinder body 20 and thepiston 22 so as to urge the piston 22 to the side for increasing theinternal volume of the fluid pressure chamber 21; a pushing shaft 24coaxially linked to the piston 22 from the side opposite to the fluidpressure chamber 21; and a gear mechanism 26 which has a gear 25coaxially screw engaged with the pushing shaft 24 through a ball screw(not shown) and which is connected to an output shaft of the electricmotor 19. The front fluid pressure-generating unit 17F can output, fromthe fluid pressure chamber 21, a fluid pressure varying according to theoperation of the electric motor 19.

The rear fluid pressure-generating unit 17R is configured in the samefashion as the front fluid pressure-generating unit 17F above, and,therefore, it is only shown in the figure with its parts correspondingto those of the front fluid pressure-generating unit 17F being denotedby the same reference symbols as used above, and with detaileddescription thereof omitted.

The front pressure-regulating unit 18F includes: a firstsolenoid-operated on-off valve 28 for switching the communication/cutoffbetween the front master cylinder MF and the front wheel brake BF; asecond solenoid-operated on-off valve 29 for switching thecommunication/cutoff between the front fluid pressure-generating unit17F and the front wheel brake BF; a stroke simulator 30 for exerting adummy reaction force according to the operating amount of the brakelever 15 on the front master cylinder MF when the firstsolenoid-operated on-off valve 28 is closed; a third solenoid-operatedon-off valve 31 for switching the communication/cutoff between thestroke simulator 30 and the front master cylinder MF; a first one-wayvalve 32 connected in parallel to the second solenoid-operated on-offvalve 29 so as to permit the flow of a brake fluid from the front fluidpressure-generating unit 17F to the side of the front wheel brake BF;and a second one-way valve 33 connected in parallel to the thirdsolenoid-operated on-off valve 31 so as to permit the flow of the brakefluid from the stroke simulator 30 to the side of the front wheel brakeBF. The pressure in the stroke simulator 30 is detected by a firstpressure sensor 34 serving as operating amount detector, the outputfluid pressure of the front master cylinder MF is detected by a secondpressure sensor 35, and the output fluid pressure of the front fluidpressure-generating unit 17F is detected by a third pressure sensor 36.

The first pressure sensor 34 obtains the operating amount of the brakelever 15 by detecting the output fluid pressure of the front mastercylinder MF when the first solenoid-operated on-off valve 28 is closed.The second pressure sensor 35 is provided for fail-safe diagnosis, and ajudgment that an abnormal state is present can be made when a differenceof not less than a predetermined value is generated between the pressuredetected by the second pressure sensor 35 and the value detected by thefirst pressure sensor 34. In addition, the value detected by the thirdpressure sensor 36 is used in a fluid pressure feedback control forcontrolling the output fluid pressure of the front fluidpressure-generating unit 17F on the basis of the value detected by thefirst pressure sensor 34.

The first solenoid-operated on-off valve 28 is a normally open typesolenoid valve, while the second and third solenoid-operated on-offvalves 29, 31 are normally closed type solenoid on-off valves. Theopening/closing operations of the first to third solenoid-operatedon-off valves 28, 29, 31 and the operations of the electric motor 19 inthe front fluid pressure-generating unit 17F are controlled by a controlunit 39 connected with a battery 38. The control unit 39 is supplied asinputs with a value detected by a front speed sensor 40F and the valuesdetected by the first to third pressure sensors 34, 35, 36. Based on thevalue detected by the front speed sensor 40F and the values detected bythe first to third pressure sensors 34 to 36, the control unit 39controls the opening/closing operations of the first to thirdsolenoid-operated on-off valves 28, 29, 31 and the operation of theelectric motor 19. In addition, an alarm lamp 41 is connected to thecontrol unit 39.

At the ignition-ON times of the motorcycle, the first solenoid-operatedon-off valve 28 is in the open state, whereas the second and thirdsolenoid-operated on-off valves 29, 31 are in the closed state, theelectric motor 19 is in the non-operative state, and the alarm lamp 41is in the ON state. When the brake lever 15 is operated to cause a fluidpressure to be outputted from the front master cylinder MF under thiscondition, the fluid pressure is exerted on the front wheel brake BFthrough the first solenoid-operated on-off valve 28.

When running of the motorcycle is started, the control unit 39 performsan initial diagnosis, and turns OFF the alarm lamp 41 if the system isjudged to be in normal condition. After the start of the running of themotorcycle, the system is put into a stand-by state, the thirdsolenoid-operated on-off valve 31 is opened, and the front mastercylinder MF is put into the state of communicating with the strokesimulator 30.

In response to the detection by the first pressure sensor 34 of a fluidpressure of not less than a predetermined value due to an operation ofthe brake lever 15 during the stand-by condition, the control unit 39closes the first solenoid-operated on-off valve 28 and opens the secondsolenoid-operated on-off valve 29. Further, the control unit 39 operatesthe electric motor 19 of the front fluid pressure-generating unit 17F,to control the output fluid pressure of the front fluidpressure-generating unit 17F, which is detected by the third pressuresensor 36, in such a manner that the output fluid pressure of the frontfluid pressure-generating unit 17F will be brought to a pressureaccording to the value detected by the first pressure sensor 34. Thisensures that the front wheel brake BF is supplied with the fluidpressure outputted from the front fluid pressure-generating unit 17Faccording to the operational load on the brake lever 15.

The rear pressure-regulating unit 18R is configured in the same fashionas the front pressure-regulating unit 18F above, and, therefore, it isonly shown in the figure with its parts corresponding to those of thefront pressure-regulating unit 18F being denoted by the same referencesymbols as used above, and with detailed description thereof omitted.Incidentally, in the fluid pressure control by the rearpressure-regulating unit 18R, the control unit 39 uses the valuedetected by the rear speed sensor 40R in place of the value detected bythe front speed sensor 40F which is used in the fluid pressure controlby the front pressure-regulating unit 18F.

In addition, by performing the fluid pressure control by the rearpressure-regulating unit 18R together with the fluid pressure control bythe front pressure-regulating unit 18F according to the operation of thebrake lever 15, the control unit 39 can carry out a rear braking forcedistribution control by which the front and rear wheel brakes BF, BR areoperated so as to exert distributed braking forces on the front wheeland the rear wheel. In addition, on the contrary, by performing thefluid pressure control by the front pressure-regulating unit 18Ftogether with the fluid pressure control by the rear pressure-regulatingunit 18R in response to the operation of the brake pedal 16, the controlunit 39 can carry out a rear braking force distribution control by whichthe front and rear wheel brakes BF, BR are operated so as to applydistributed braking forces to the front wheel and the rear wheel.

In FIG. 2, the body frame F of the motorcycle includes a head pipe 45,on which a front fork 43, and a steering handle 44 operatively connectedto the front fork 43 are pivotally supported. The front fork rotatablysupports the front wheel WF thereon, equipped with the front wheel brakeBF.

The body frame F also includes a left-right pair of main frame sections46 . . . extending rearwardly downwards from the head pipe 45; centerframe sections 47 . . . connected respectively to corresponding rearparts of the main frame sections 46 . . . left and right pivot plates 48. . . integrally connected to the center frame sections 47 . . . andextending downwards; and a left-right pair of seat rails 49 . . .respectively connected to rear parts of the center frame sections 47 . .. and extending rearwardly upwards.

The main frame sections 46 . . . are integrally provided with enginehangers 50 . . . extending downwards. An engine body 51 of an engine Eof the in-line four-cylinder type, for example, is supported by lowerparts of the engine hangers 50 . . . , the center frame sections 47 . .. and the pivot plates 48 . . . , in such an attitude that the cylinderaxis thereof is inclined forwardly upwards.

The engine body 51 includes: a crankcase 53; a cylinder block 54 risingat a forwardly upward inclination from the crankcase 53; and a cylinderhead 52 connected to an upper part of the cylinder block 54.

A fuel tank 55 is mounted on both the main frame sections 46 . . . onthe upper side of the engine body 51. In addition, an upwardly extendingintake system 57 is connected to a rear surface of the cylinder head 52of the engine body 51, and an air cleaner 56 that the intake system 57has at its upstream end is so disposed as to be covered with the fueltank 55. On the other hand, an exhaust system 58 connected to a frontsurface of the cylinder head 52 includes: a plurality of exhaust pipes59 . . . which are connected to the front surface of the cylinder head52 in the manner of corresponding respectively to the cylinders andwhich extend downwards from the cylinder head 52; and an exhaust muffler60 disposed between rear parts of both the seat rails 49 . . . in thestate of being connected to the exhaust pipes 59 . . . . Moreover, theexhaust pipes 59 . . . have inclined parts 59 a extending forwardlydownwards from the front surface of the cylinder head 52, and curvedparts 59 b curved from lower parts of the inclined parts 59 a . . .toward the lower side of the engine body 51, so that a space triangularin shape in side view is formed between the exhaust pipes 59 and thefront surface of the engine body 51. Furthermore, on the front side ofthe engine body 51, a radiator 61 is fixedly disposed so as to belocated on the skew upper side of the exhaust pipes 59 . . . .

On the pivot plates 48 . . . of the body frame F, a front end part of aswing arm 62 rotatably supporting the rear wheel WR (which is equippedwith the rear wheel brake BR) on its rear end parts is verticallyswingably borne. A link mechanism 63 is provided between afront-end-side lower part of the swing arm 62 and lower parts of thepivot plates 48, and a lower end part of a shock absorber 65 connectedat its upper end part to the swing arm 62 and extending vertically isconnected to a link member 64 constituting a part of the link mechanism63.

In addition, an output from a transmission (not shown) incorporated inthe crankcase 53 possessed by the engine body 51 is transmitted to therear wheel WR through chain-type power transmission unit 67 having anendless chain 66.

A riders' seat 68 is provided on the seat rails 49 . . . so as to bedisposed on the rear side of the fuel tank 55. The riders' seat 68includes a front seat 69 on which to seat the driver, and a rear seat 70on which to seat the passenger and which is spaced to the rear side fromthe front seat 69. Pillion steps 71 on which to rest the feet of thepassenger seated on the rear seat 70 are fastened to outside surfaces ofintermediate parts of the seat rails 49 . . . .

A part of the body frame F and the engine E are covered with a frontcowl 72 formed from a synthetic resin. The front cowl 72 includes afront cover part 73 for covering the head pipe 45 on the front side, andside covers 74 . . . which are in connection with the front cover 73 andwhich cover the engine body 51, the exhaust pipes 59 . . . of theexhaust system 58, and the radiator 61 on both lateral sides.

In the motorcycle as above, the front fluid pressure-generating unit17F, the front pressure-regulating unit 18F, the rear fluidpressure-generating unit 17R, the rear pressure-regulating unit 18R andthe control unit 39 are disposed in the vicinity of the engine E, i.e.,in the vicinity of the center of the vehicle body.

Now, a structure for arrangement of the front fluid pressure-generatingunit 17F, the front pressure-regulating unit 18F, the rear fluidpressure-generating unit 17R, the rear pressure-regulating unit 18R, andthe control unit 39 in the motorcycle, and the operations and effects ofthe structure, will be sequentially described below.

Front Pressure-Regulating Unit 18 f

An arrangement structure of the front pressure-regulating unit 18F willbe described referring to FIGS. 3 to 7. First, in FIG. 3, the firstsolenoid-operated on-off valve 28, the second solenoid-operated on-offvalve 29, the stroke simulator 30, the third solenoid-operated on-offvalve 31, the first one-way valve 32, and the second one-way valve 33which constitute the front pressure-regulating unit 18F are arranged ona base 77 formed in a rectangular parallelepiped, or box shape bycasting of a light metal such as an aluminum alloy.

Projecting parts of the first solenoid-operated on-off valve 28, thesecond solenoid-operated on-off valve 29, the third solenoid-operatedon-off valve 31, the first one-way valve 32 and the second one-way valve33 which are projecting from the base 77 are covered by a syntheticresin-made cover 78 integrally provided with a coupler part 78 a. Thefirst to third pressure sensors 34 to 36 are also arranged on the base77, and projecting parts of the first to third pressure sensors 34 to 36which are projecting from the base 77 are also covered with the cover78.

Referring to FIGS. 4 to 7 also, the front pressure-regulating unit 18Fis arranged in a position which is on the rear side of the intake system57 being connected to the cylinder head 52 of the engine body 51 mountedon the body frame F and being extended upwards from the cylinder head 52and which is between the engine body 51 and the fuel tank 55 disposed onthe upper side of the engine body 51. The front pressure-regulating unit18F is floatingly supported, through an elastic case 79 covering thepressure-regulating unit 18F, on support unit 83 supported on the bodyframe F.

The elastic case 79 includes lower and upper case members 80, 81provided as bisected lower and upper parts so as to clamp the frontpressure-regulating unit 18F in such an attitude as to have the base 77located on the upper side. Both the case members 80, 81 are formed of anelastic material, for example, a rubber.

The lower case member 80 is formed in a box-like shape open to the upperside so that the cover 78 of the front pressure-regulating unit 18F canbe fitted therein, and the upper case member 81 is formed in a box-likeshape open to the lower side so that the base 77 of the frontpressure-regulating unit 18F can be fitted therein. Moreover, the uppercase member 81 is provided with a cutout 82 for permitting the coupler78 a of the cover 78 to project therethrough. In addition, of both thecase members 80 and 81, at least the lower case member 80 is integrallyand projectingly provided at its inner surface, in this embodiment, boththe case members 80 and 81 are integrally and projectingly provided attheir inner surface, with a plurality of projections 80 a . . . , 81 a .. . put into the pressure-regulating unit 18F.

The support unit 83 is composed in a cage-like form by use of a lowercage body 84 which is attached to the body frame F so as to coversubstantially the whole perimeter of a lower part of the frontpressure-regulating unit 18F and to support the frontpressure-regulating unit 18F on the lower side of the latter, and anupper cage body 85 which is fastened to the lower cage body 84.

The lower cage body 84 has a plurality of bent, small-width metallicplate materials connected to each other. Specifically, the lower cagebody 84 includes: a cage part 84 a surrounding substantially the wholeperimeter of the lower part of the front pressure-regulating unit 18F;two support plate parts 84 b, 84 c connected to the cage part 84 a so asto support the front pressure-regulating unit 18F on the lower side ofthe latter; three support arm parts 84 d, 84 e, 84 f extending outwardlysideways from the cage body 84 a; and two attaching projected parts 84g, 84 h projected from the cage body 84 a so as to fasten the upper cagebody 85 thereto.

The front pressure-regulating unit 18F, together with the lower casemember 80 fitted in a lower part thereof, is fitted into and supportedby the cage part 84 a and both the support plate parts 84 b, 84 c of thelower cage body 84.

The support arm parts 84 d, 84 e, 84 f are extended to the side of theleft-side main frame section 46 and the left-side center frame section47, of both the main frame sections 46 . . . and both the center framesections 47 . . . of the body frame F. The support arm part 84 d isfastened to the engine hanger 50 integral with the main frame section 46by a bolt 86, the support arm part 84 e is fastened to the main framesection 46 on the rear side relative to the engine hanger 50 by a bolt87, and the support arm part 84 f is fastened to the center framesection 47 by a bolt 88.

The upper frame body 85 is brought from above into contact with theupper case member 81 fitted from above into an upper part, or the base77, of the front pressure-regulating unit 18F, and is fastened to boththe attaching projected parts 84 g, 84 h of the lower frame body 84. Theupper frame body 85 integrally includes: a presser part 85 a put intocontact with the upper case member 81 from above; and a pair ofattaching leg parts 85 b, 85 c extended from the presser part 85 atoward the sides of both the attaching projected parts 84 g, 84 h.

On the other hand, weld nuts 89 . . . are firmly attached to the lowersurfaces of both the attaching projected parts 84 g, 84 h of the lowerframe body 84. Bolts 90, 90 passed through tip parts of both theattaching leg parts 85 b, 85 c and through both the attaching projectedparts 84 g, 84 h are screw engaged with the weld nuts 89 . . . andtightened, whereby the upper frame body 85 is fastened to the lowerframe body 84. As a result, the support unit 83 is composed in a frameform by use of the lower frame body 84 which is attached to the bodyframe F so as to cover substantially the whole perimeter of the lowerpart of the front pressure-regulating unit 18F and to support the frontpressure-regulating unit 18F on the lower side of the latter, and theupper frame body 85 fastened to the lower frame body 84. In addition,the front pressure-regulating unit 18F is clamped between the lowerframe body 84 and the upper frame body 85, with the lower case member 80and the upper case member 81 (which are formed of an elastic material)interposed therebetween.

Moreover, the front pressure-regulating unit 18F is disposed on theupper side of and in proximity to a cooling pipe (not shown)constituting a part of a cooling water circulation circuit provided forthe engine E. In view of this, the lower case member 80 is provided inits lower surface with a recessed part 80 b which is curved to the upperside in order to obviate interference with the cooling water pipe,whereby a cooling effect on the front pressure-regulating unit 18F owingto the arrangement of the unit in proximity to the cooling water pipecan be obtained.

According to the arrangement structure of the front pressure-regulatingunit 18F as above, the front pressure-regulating unit 18F is covered bythe elastic case 79, so that the influence of the heat from the engine Ecan be prevented from being exerted on the front pressure-regulatingunit 18F. In addition, since the front pressure-regulating unit 18F isfloatingly supported through the elastic case 79 on the support unit 83supported on the body frame F, transmission of vibrations from theengine E to the front pressure-regulating unit 18F can be suppressed.

Moreover, the front pressure-regulating unit 18F is arranged in aposition which is on the rear side of the intake system 57 beingconnected to the cylinder head 52 of the engine body 51 mounted on thebody frame F and being extended upwards from the cylinder head 52 andwhich is between the engine body 51 and the fuel tank 55 disposed on theupper side of the engine body 51. This ensures that the frontpressure-regulating unit 18F is disposed at such a position as to beless liable to be exposed to the radiant heat from the exhaust system 58of the engine E, whereby the influence of the heat from the engine Eupon the front pressure-regulating unit 18F can be effectivelyrestrained. In addition, the front pressure-regulating unit 18F is laidout in a comparatively large vacant space on the rear side of the intakesystem 57, whereby the influence of the front pressure-regulating unit18F upon the layout of other component parts can be minimized.

In addition, the elastic case 79 is composed of the elasticmaterial-made lower and upper case members 80, 81 provided as bisectedlower and upper parts so as to clamp the front pressure-regulating unit18F from the lower and upper sides, and, at least the lower case member80 of both the case members 80 and 81, in this embodiment, both of thecase members 80 and 81 are integrally and projectingly provided at theirinner surfaces with the plurality of projected parts 80 a . . . , 81 a .. . put into contact with the front pressure-regulating unit 18F.Therefore, the front pressure-regulating unit 18F can be floatinglysupported assuredly while facilitating the operation of containing thefront pressure-regulating unit 18F into the elastic case 79.

Furthermore, the front pressure-regulating unit 18F is floatinglysupported, through the lower and upper case members 80 and 81 of theelastic case 79, on the support unit 83 mounted to the body frame F. Inaddition, the support unit 83 is composed in a frame form by use of thelower frame body 84 which is attached to the body frame F so as to coversubstantially the whole perimeter of the lower part of the frontpressure-regulating unit 18F and to support the frontpressure-regulating unit 18F on the lower side of the latter, and theupper frame body 85 which is fastened to the lower frame body 84.Moreover, the front pressure-regulating unit 18F is clamped between thelower frame body 84 and the upper frame body 85, with the lower andupper case members 80 and 81 therebetween. Therefore, by a simpleprocess in which the front pressure-regulating unit 18F is mounted tothe lower frame body 84 attached to the body frame F through the lowercase member 80 and then the upper frame body 85 with the upper casemember 81 interposed between itself and the front pressure-regulatingunit 18F is attached to the lower frame body 84, the frontpressure-regulating unit 18F can be floatingly supported on the supportunit 83 mounted to the body frame F. Thus, the mounting operation isfacilitated.

Front Fluid Pressure-Generating Unit 17F

An arrangement structure of the front fluid pressure-generating unit 17Fwill be described referring to FIGS. 8 to 13. First, as shown in FIG. 2,the front fluid pressure-generating unit 17F is arranged between theengine body 51 and the exhaust pipes 59 . . . extended downwards fromthe front surface of the cylinder head 52 in the engine body 51.Moreover, the exhaust pipes 59 . . . include the inclined parts 59 a . .. which extends forwardly downwards from the front surface of thecylinder head 52, and the curved parts 59 b . . . which are curved fromthe lower parts of the inclined parts 59 a . . . toward the lower sideof the engine body 51, in such a manner that a space rectangular inshape in side view is formed between themselves and the front surface ofthe engine body 51, with the front fluid pressure-generating unit 17Fbeing arranged in the space. Furthermore, the front fluidpressure-generating unit 17F is arranged on the rear lower side of theradiator 61 which is supported on the body frame F on the front side ofthe engine body 51.

In FIG. 8, the front fluid pressure-generating unit 17F is supported,through support unit 93, on the engine hangers 50 . . . provided to beintegral with the left-right pair of main frame sections 46 which extendrearwardly downwards from the head pipe 45 and which constitute a partof the body frame F. The support unit 93 is composed in a frame form byuse of a first support frame 94 which is attached to the engine hangers50 . . . and which extends in the left-right direction on the rear sideof the front fluid pressure-generating unit 17F, and a second supportframe 95 which is attached to the first support frame 94 in such amanner as to surround the front fluid pressure-generating unit 17F fromthe front side of the latter.

Referring to FIG. 9 also, a weld nut 96 is securely attached to the rearsurface of an intermediate part in the width direction of the firstsupport frame 94, and a weld nut 97 is secured to the rear surface of atip part of a support arm part 94 a branched skewly downward from aleft-side end part (in FIG. 8, a right-side end part) of the firstsupport frame 94 as viewed from a person facing in the running (forward)direction of the motorcycle. One end part of the second support frame 95is fastened to the intermediate part in the width direction of the firstsupport frame 94 by a bolt 98 screw engaged with the weld nut 96, andthe other end part of the second support frame 95 is firmly attached tothe tip part of the support arm part 94 a of the first support frame 94by a bolt 99 screw engaged with the weld nut 97.

Referring to FIG. 10 also, while the brackets 53 a . . . provided at thecrankcase 53 of the engine body 51 are fastened to the engine hangers 50. . . provided to be integral with the main frame sections 46 . . .through bolts 105, attaching members 102 . . . clamped between thebrackets 53 a . . . and the engine hangers 50 . . . are co-fastened tothe engine hangers 50 . . . together with the brackets 53 a . . . by thebolts 105.

On the other hand, both end parts of the first support frame 94 arefitted with rubber bushings 100, 100. Collars 101 . . . provided attheir one-side ends with flange parts 101 a . . . projecting outwardsare inserted in the rubber bushings 100 . . . , and the flange parts 101a . . . are put in abutment on the attaching members 102 . . . . Inaddition, washers 103 . . . are put in contact with the other-side endsof the collars 101 . . . so that the collars 101 . . . are clampedbetween the washers 103 . . . and the attaching members 102 . . . , andbolts 104 . . . passed through the washer 103 . . . and the collars 101. . . are screw engaged with the attaching members 102 . . . . Thus,both left and right end parts of the first support frame 94 of thesupport unit 93 are fastened to the engine hangers 50 . . . of theleft-right pair of main frame sections 46 . . . , by co-fasteningthereof together with the brackets 53 a . . . of the crankcase 53 in theengine body 51.

Referring to FIG. 11 also, an attaching arm 106 extending upwards issecurely attached to an intermediate part in the left-right direction ofthe first support frame 94. A rubber bushing 107 is mounted to an upperend part of the attaching arm 106, and a collar 108 provided at its oneend with a flange part 108 a projecting outwards is passed through therubber bushing 107. On the other hand, the cylinder block 54 of theengine body 51 is provided with a support boss part 54 a for contactwith the flange part 108 a. A washer 109 is put in contact with theother end of the collar 108 so as to clamp the collar 108 between itselfand the support boss part 54 a, and a bolt 110 passed through the washer109 and the collar 108 is screw engaged with the support boss part 54 a.

Referring to FIG. 12 also, a support bar 111 extending downwards issecured to an intermediate part in the left-right direction of the firstsupport frame 94. The support bar 111 is fitted in a rubber bushing 112mounted to the crankcase 53 of the engine body 51.

Thus, both the left and right end parts of the first support frame 94 ofthe support unit 93 are supported on the engine hangers 50 . . . of themain frame sections 46 . . . through the rubber bushings 100 . . . , andthe intermediate part in the left-right direction of the first supportframe 94 is supported on the engine body 51 through the rubber bushings107, 112.

The front fluid pressure-generating unit 17F is elastically supported bythe support member 93, and a support plate 116 opposed from the frontside to a bracket 115 provided at a left side part of the front fluidpressure-generating unit 17F is firmly attached to the first supportframe 94 of the support unit 93.

In FIG. 13, a rubber bushing 117 is mounted to the support plate 116,and a collar 118 provided at its one end with a flange part 118 aprojecting outwards is passed through the rubber bushing 117 so that theflange part 118 a makes contact with the bracket 115. In addition, awasher 119 is put in contact with the other end of the collar 118 so asto clamp the collar 118 between itself and the bracket 115, and a bolt120 passed through the washer 119 and the collar 118 is screw engagedwith the bracket 115.

In addition, the second support frame 95 is provided with a supportplate part 121 which is opposed to the front fluid pressure-generatingunit 17F from the lower side, and a support plate 122 which is opposedto the front fluid pressure-generating unit 17F from the left side.Rubber bushings 123, 124 mounted to the support plate parts 121, 122 areattached to the front fluid pressure-generating unit 17F through bolts125, 126 by use of the same structure as that shown in FIG. 13.

In short, the front fluid pressure-generating unit 17F is supported onthe support unit 93 through the rubber bushings 117, 123, and 124.

According to the arrangement structure of the front fluidpressure-generating unit 17F as above, the front fluidpressure-generating unit 17F is arranged between the engine body 51 andthe exhaust pipes 59 . . . extended downwards from the cylinder head 52.Therefore, the front fluid pressure-generating unit 17F can be laid outby utilizing effectively the vacant space which is on the front side ofthe engine body 51 and on the lower side of the exhaust pipes 59 . . . ,whereby concentration of mass can be contrived. Moreover, although theheat from the exhaust pipes 59 . . . reaches the front fluidpressure-generating unit 17F, the running airflow generated by therunning of the motorcycle comes into contact with the front fluidpressure-generating unit 17F, so that the temperature of the front fluidpressure-generating unit 17F can be prevented from rising excessively.In addition, since the support unit 93 for supporting the front fluidpressure-generating unit 17F is supported through the rubber bushings100 . . . , 107, 112 on the engine body 51 and the engine hangers 50 . .. of the main frame sections 46 . . . constituting a part of the bodyframe F, transmission of vibrations from the engine E to the front fluidpressure-generating unit 17F can also be restrained.

In addition, the cylinder head 52 is connected to an upper part of thecylinder block 54 rising at a forwardly upward inclination from thecrankcase 53. The exhaust pipes 59 . . . connected to the front surfaceof the cylinder head 52 have the inclined surfaces 59 a . . . extendingforwardly downwards from the front surface of the cylinder head 52, andthe curved parts 59 b . . . curved from the lower parts of the inclinedparts 59 a . . . toward the lower side of the engine body 51, and aspace triangular in shape in side view is formed between the exhaustpipes 59 . . . and the front surface of the engine body 51. Moreover,the front fluid pressure-generating unit 17F is laid out in the space.Therefore, since a comparatively large space can be secured between theexhaust pipes 59 . . . and the front surface of the engine body 51, therunning airflow can easily flow in the surroundings of the front fluidpressure-generating unit 17F disposed in the space, and the temperatureof the front fluid pressure-generating unit 17F can be effectivelyprevented from rising excessively.

In addition, both the left and right end parts of the first supportframe 94 in the support unit 93 are supported on the engine hangers 50 .. . of the left-right pair of main frame sections 46 . . . through therubber bushings 100 . . . , and the intermediate part in the left-rightdirection of the first support frame 94 is supported on the engine body51 through the rubber bushings 107, 112, so that the front fluidpressure-generating unit 17F can be floatingly supported while enhancingthe rigidity of the support unit 93.

In addition, since both the left and right end parts of the support unit93 are fastened to the engine hangers 50 . . . of the main framesections 46 . . . by co-fastening thereof together with the brackets 53a . . . of the crankcase 53 of the engine body 51, a reduction in thenumber of component parts and a reduction in the number of working stepscan be contrived.

In addition, the support unit 93 is composed in a frame form by use ofthe first support frame 94 which is attached to the engine hangers 50 .. . of the main frame sections 46 . . . and which extends in theleft-right direction on the rear side of the front fluidpressure-generating unit 17F, and the second support frame 95 which isattached to the first support frame 94 in such a manner as to surroundthe front fluid pressure-generating unit 17F from the front side.Therefore, the front fluid pressure-generating unit 17F can be supportedin such a manner that the front fluid pressure-generating unit 17F caneasily receive the running airflow.

Furthermore, since the front fluid pressure-generating unit 17F is laidout on the rear lower side of the radiator 61 supported by the bodyframe F on the front side of the engine body 51, the front fluidpressure-generating unit 17F can be protected by the radiator 61 and theexhaust pipes 59 . . . from foreign matters such as flying stones comingfrom the front side.

Rear Pressure-Regulating Unit 18R

An arrangement structure of the rear pressure-regulating unit 18R willbe described referring to FIGS. 2 and 14 to 16. First, as shown in FIG.2, the rear pressure-regulating unit 18R is arranged on the rear side ofthe engine body 51 and between an upper end part of the shock absorber65 and the engine body 51. The rear pressure-regulating unit 18R issupported by a support member 130, as shown in FIGS. 14 and 15.

The support member 130 includes: a support member main part 130 a whichis arranged between both the center frame sections 47, 47 while having apart thereof opposed from above to the rear pressure-regulating unit 18Rdisposed on the lower side of a crossmember 131 with a base part 77located on the rear side and with a cover 78 located on the front side;attaching arm parts 130 b, 130 c, 130 d extended from the support membermain part 130 a so as to be opposed to both the center frame sections47, 47 and the back surface of the crossmember 131; and a pair ofsupport arm parts 130 e, 130 f drooping from the support member mainpart 130 a so as to be located on both the left and right sides of therear pressure-regulating unit 18R.

Rubber bushings 132, 133, and 134 are mounted to tip parts of theattaching arm parts 130 b, 130 c, and 130 d. Collars 135, 136, and 137provided at their one-side ends with flange parts 135 a, 136 a, and 137a projecting outwards are passed through the rubber bushings 132 to 134so that the flange parts 135 a to 137 a make contact with the centerframe sections 47, 47 and the back surface of the crossmember 131. Inaddition, washers 138, 139, and 140 are put in contact with theother-side ends of the collars 135 to 137 so that the collars 135 to 137are clamped between them and the center frame sections 47, 47 and thecrossmember 131. Bolts 141, 142, and 143 passed through the washers 138to 140 and the collars 135 to 137 are screw engaged with the centerframe sections 47, 47 and the crossmember 131.

A frame member 145 is attached to an upper part of the base 77 of therear pressure-regulating unit 18R by three bolts 146, 146, and 146, forexample. The frame member 145 is disposed between the support membermain part 130 a and both the support arm parts 130 e, 130 f of thesupport member 130, and the rear pressure-regulating unit 18R. Threeportions of the frame member 147 are supported respectively on thesupport member main part 130 a and both the support arm parts 130 e, 130f through rubber bushings 147 . . . . Specifically, the upper part ofthe rear pressure-regulating unit 18R is attached to the support member130 through the rubber bushings 147 . . . so as to be suspended from thesupport member 130.

In FIG. 16, the rubber bushings 147 . . . are mounted respectively tothe support member main part 130 a and both the support arm parts 130 e,130 f of the support member 130, and weld nut 148 are securely attachedto the frame member 145 in the manner of corresponding to the rubberbushings 147 . . . . In addition, collars 149 . . . provided at theirone-side ends with flange parts 149 a projecting outwards are passedthrough the rubber bushings 147 . . . so that the flange parts 149 a areclamped between them and the support member main part 130 a and both thesupport arm parts 130 e, 130 f. In addition, washers 150 . . . are putin contact with the other-side ends of the collars 149 . . . so that thecollars 149 . . . are clamped between them and the support member mainpart 130 a and both the support arm parts 130 e, 130 f, and bolts 151 .. . passed through the washer 150 . . . and the collars 149 . . . arescrew engaged with the weld nuts 148 . . . .

According to the arrangement structure of the rear pressure-regulatingunit 18R as above, the support member 130 for supporting the rearpressure-regulating unit 18R is floatingly supported by the pair ofcenter frame sections 47 . . . disposed on both the left and right sidesof the engine body 51 and by the crossmember 131 for connecting thecenter frame section 47 . . . to each other on the rear side of theengine body 51 in such a manner as to constitute a part of the bodyframe F together with the center frame sections 47 . . . , through therubber bushings 132, 133, and 134. Therefore, vibrations transmittedfrom the engine E can be prevented from reaching the rear wheelpressure-regulating unit 18R. Moreover, the rigidity of the supportmember 130 can be set to a level sufficient to hold the rear wheelpressure-regulating unit 18R, without being affected by the rigidity onthe side of the body frame F, which makes it unnecessary to enhance thestrength of the support member 130 more than required. Thus, reductionsin weight and cost can be contrived.

In addition, since the upper part of the rear wheel pressure-regulatingunit 18R is so attached as to be suspended from the support member 130,the position of the rear wheel pressure-regulating unit 18R in the widthdirection of the body frame F can easily be conditioned so as not tointerfere with other component parts.

Further, the rear wheel pressure-regulating unit 18R is arranged betweenthe engine body 51 and the upper end part of the shock absorber 95provided between the swing arm 62 and the link member 64, whichconstitutes a part of the link mechanism 63 provided between the swingarm 62 and the body frame F. Therefore, the rear wheelpressure-regulating unit 18R can be effectively laid out in the spacebetween the engine body 51 and the upper end part of the shock absorber65. Moreover, the rear wheel pressure-regulating unit 18R can beprotected by surrounding the left and right sides and the front and rearsides of the rear wheel pressure-regulating unit 18R with the body frameF, the engine body 51 and the shock absorber 65.

Rear Fluid Pressure-Generating Unit 17R

An arrangement structure of the rear fluid pressure-generating unit 17Rwill be described referring to FIGS. 17 to 21. First, as shown in FIGS.17 and 18, the rear fluid pressure-generating unit 17R is supported onthe left-right pair of seat rails 49 . . . constituting a part of thebody frame F; in plan view, it is arranged between both the seat rails49, 49 at a position nearer to the left-side seat rail 49 of both theseat rails 49 . . . .

Referring to FIGS. 19 and 20 also, a first support member 154 isattached to the left-side seat rail 49 of both the seat rails 49 . . . ,and the rear fluid pressure-generating unit 17R is floatingly supportedby the first support member 154 and a crossmember 155 for connectionbetween both the seat rails 49 . . . , through rubber bushings 156 . . ..

Both end parts of the crossmember 155 are connected to the seat rails 49. . . by pairs of bolts 157, 157 . . . . In addition, the first supportmember 154 is fastened to the left-side seat rail 49 by a pair of bolts158, 158.

A second support member 159 is secured to the crossmember 155, and anattaching member 160 fixed to the rear fluid pressure-generating unit17R is supported on the second support member 159 through a rubberbushing 156.

Referring to FIG. 21 also, the attaching member 160 is firmly attachedto the cylinder body 20 of the rear fluid pressure-generating unit 17Rby a pair of screw members 161, 161, and the rubber bushing 156 ismounted to the attaching member 160. In addition, a weld nut 162 issecurely attached to the second support member 159 at a positioncorresponding to the rubber bushing 156. A collar 163 provided at itsone end with a flange part 163 a projecting outwards is passed throughthe rubber bushing 156 so as to put the flange part 163 a in contactwith the second support member 159. In addition, a washer 164 is put incontact with the other end of the collar 163 so as to clamp the collar163 between itself and the second support member 159, and a bolt 165passed through the washer 164 and the collar 163 is screw engaged withthe weld nut 162.

In addition, a support plate part 154 a opposed to the rear fluidpressure-generating unit 17R from the outer side is provided at a frontpart of the first support member 154, and a support plate part 154 bopposed to the rear fluid pressure-generating unit 17R from the rearside is provided at a rear part of the first support member 154. Therubber bushings 156, 156 mounted respectively to these support plateparts 154 a, 154 b are attached to the rear fluid pressure-generatingunit 17R with bolts 166, 167, by the same attaching structure as thatdescribed referring to FIG. 21 above.

Meanwhile, a sub-tank 168 for adjusting the damping force of the shockabsorber 65, provided between the swing arm 62 and the link member 64 ofthe link mechanism 63, is arranged on the rear side of the rear fluidpressure-generating unit 17R. The sub-tank 168 is supported by theleft-side seat rail 49.

Specifically, a sub-tank support member 169 for supporting the sub-tank168 is fixed to the left-side seat rail 49. The sub-tank support member169 is fixed to the left-side seat rail 49 with a pair of bolts 170, 170by co-fastening thereof together with the pillion step 71.

According to the arrangement structure of the rear fluidpressure-generating unit 17R as above, the rear fluidpressure-generating unit 17R is supported by the left-right pair of seatrails 49, 49 in such a manner as to be laid out between both the seatrails 49 . . . in plan view. Therefore, the rear fluidpressure-generating unit 17R can be laid out in the vicinity of the rearpressure-regulating unit 18R, which is disposed on the rear side of theengine body 51, and in a place where it is easy to secure the spacenecessary for disposing the rear fluid pressure-generating unit 17R.

In addition, the rear fluid pressure-generating unit 17R is floatinglysupported by the first support member 154 which is attached to theleft-side seat rail 49 of both the seat rails 49 . . . and by thecrossmember 155 for connection between both the seat rails 49 . . . ,through the rubber bushings 156 . . . . Therefore, vibrations on theside of the body frame F can be restrained from reaching the rear fluidpressure-generating unit 17R.

In addition, the sub-tank 168 for adjusting the damping force of theshock absorber 65 is disposed on the rear side of the rear fluidpressure-generating unit 17R and is supported by the left-side seat rail49. Therefore, it is possible to lay out the rear fluidpressure-generating unit 17R between the sub-tank 168 and the enginebody 51, and thereby to protect the rear fluid pressure-generating unit17R from external forces.

Furthermore, since the sub-tank support member 169 for supporting thesub-tank 168 is fixed to the left-side seat rail 49 by co-fasteningthereof together with the pillion step 71, the number of component partscan be reduced.

Control Unit 39

An arrangement structure of the control unit 39 will be describedreferring to FIGS. 22 to 25. The control unit 39 is arranged on the leftside of the engine body 51 mounted on the body frame F. Moreover, inorder to enhance the property for “knee gripping” by the driver, thecontrol unit 39 is disposed on the inner side relative to the vehiclebody side ends of that portion of the motorcycle at which the vehiclewidth is the largest. The control unit 39 is contained in and supportedby a synthetic resin-made control unit support case 171 interposedbetween the control unit 39 and the engine body 51, and is covered withthe side cover part 74 constituting a part of the front cowl 72.

The control unit support case 171 is formed in a box-like shape openedon the side opposite to the engine body 51 so as to contain the controlunit 39 on the side opposite to the engine body 51. Meanwhile, the frontpressure-regulating unit 18F supported on the body frame F through thesupport unit 83 is arranged on the inner side relative to the controlunit support case 171, and an upper part of the control unit supportcase 171 is attached to the support arm parts 84 e, 84 f possessed bythe lower frame body 84 constituting a part of the support unit 83, bybolts 172, 173. Specifically, as clearly shown in FIG. 25, weld nuts 178. . . are secured to the support arm parts 84 e, 84 f, and the bolts172, 173 passed through the control unit support case 171 and thesupport arm parts 84 e, 84 f are screw engaged with the weld nuts 178 .. . .

Meanwhile, a crankcase cover 174 such as a generator cover is fastenedto a left side surface of the crankcase 53 constituting a part of theengine body 51, by a plurality of bolts 175, 175 . . . . To a lowersupport member 176 which is co-fastened to the crankcase 53 togetherwith the crankcase cover 174 by use of one of the bolts 175, 175 . . . ,a lower part of the above-mentioned control unit support case 171 isattached by a pair of bolts 177, 177. Specifically, as clearly shown inFIG. 25, a pair of weld nuts 179 . . . are firmly attached to the lowersupport member 176, and the bolts 177 . . . passed through the controlunit support case 171 and the lower support member 176 are screw engagedwith the weld nuts 179.

The control unit 39 is contained in the control unit support case 171with, for example, three elastic members 181 . . . interposed betweenitself and the control unit support case 171. The control unit 39 issupported on the control unit support case 171 through a fixing member182 which is put in elastic contact with an outside surface of thecontrol unit 39 along the front-rear direction of the body frame F andwhich is detachably attached to the control unit support case 171. Thefixing member 182 may be, for example, an endlessly continuous rubberstring, which is disengageably engaged with lock parts 182, 182 providedat the control unit support case 171 at positions on the front and rearsides of the control unit 39.

The control unit support case 171 is provided with a running airflowleading-in part 184 for permitting the running airflow to pass to theside of the control unit 39, the running airflow inlet port 184 beinglocated on the lower front side of the control unit 39, and also with arunning airflow leading-out part 185 for leading out the running airflowhaving passed through the lateral sides of the control unit 39, therunning airflow leading-out part 185 being located on the upper rearside of the control unit 39.

The side cover part 74 of the front cowl 72 covers the control unit 39,with a cushion member 186 between itself and a lower part of the controlunit support case 171. The side cover part 74 is provided with a runningairflow intake port 187 at its portion corresponding to the runningairflow leading-in part 184, and with running airflow exhaust ports 188,189, and 190 at its portions corresponding to the running airflowleading-out part 185.

According to the arrangement structure of the control unit 39 as above,the control unit 39 arranged on a lateral side of the engine body 51 iscontained in and supported by the control unit support case 171interposed between the control unit 39 and the engine body 51.Therefore, direct reach of the heat from the engine body 51 to thecontrol unit 39 can be avoided by the control unit support case 171interposed between the control unit 39 and the engine body 51, whilepermitting the control unit 39 to be disposed in the vicinity of theengine body 51.

Moreover, the running airflow leading-in part 184 for permitting therunning airflow to pass to the side of the control unit 39 is formed ata front part of the control unit support case 171, and the runningairflow leading-out part 185 for leading out the running airflow havingpassed through the lateral sides of the control unit 39 is formed at arear part of the control unit support case 171. Therefore, duringrunning of the motorcycle, the running airflow can be caused to passthrough the lateral sides of the control unit 39, thereby cooling thecontrol unit 39.

In addition, an upper part of the control unit support case 171 isattached to the support arm parts 84 e, 84 f possessed by the supportunit 39 for supporting the front pressure-regulating unit 18F on thebody frame F. Therefore, the component parts and members for supportingthe front pressure-regulating unit 18F and the control unit support case171 onto the body frame F can be made to be suited to common use, whichcontributes to a reduction in the number of component parts.

In addition, a lower part of the control unit support case 171 isattached to the lower support member 176 which is co-fastened to thecrankcase 53 together with the crankcase cover 174 fastened to one sideof the crankcase. Therefore, the bolts 175 for fastening the lowersupport member 176 to the side of the crankcase 53 can be used in commonto the fastening of the crankcase cover 174, which contributes to areduction in the number of component parts.

In addition, the control unit 39 accompanied by the plurality of elasticmembers 181 . . . interposed between itself and the control unit supportcase 171 is supported on the control unit support case 171 by the fixingmember 182 which is put in elastic contact with the outside surface ofthe control unit 39 along the front-rear direction of the body frame Fand which is detachably attached to the control unit support case 171.Therefore, the fixing member 182 can be attached and detached easily,whereby maintainability of the control unit 39 can be enhanced.

Furthermore, the control unit 39 is covered with the side cover part 74constituting a part of the front cowl 72, and the running airflow intakeport 187 and the running airflow exhaust ports 188, 189, and 190 areprovided at portions corresponding to the running airflow leading-inpart 184 and the running airflow leading-out part 185 of the side coverpart 74. Therefore, the running airflow can be introduced from theexterior into the running airflow leading-in part 184 and can beexhausted from the running airflow leading-out part 185, wherebyperformance of cooling the control unit 39 is maintained, and, at thesame time, the control unit 39 is covered with the side cover part 74,whereby the control unit 39 can be protected from externally comingforeign matter, rainwater, etc.

While the embodiment of the present invention has been described above,the invention is not limited to the embodiment, and various designmodifications are possible without departure from the invention asdescribed in claims.

Although the present invention has been described herein with respect toa number of specific illustrative embodiments, the foregoing descriptionis intended to illustrate, rather than to limit the invention. Thoseskilled in the art will realize that many modifications of theillustrative embodiment could be made which would be operable. All suchmodifications, which are within the scope of the claims, are intended tobe within the scope and spirit of the present invention.

1. A motorcycle comprising: a body frame comprising left and right seatrails which are spaced apart from one another and provided to support aseat thereon; an engine mounted on said body frame, said enginecomprising an engine body; a wheel brake; a manually operable brakeoperating element which is fluidly connected to said wheel brake; and abrake-by wire system comprising: an operation amount detector fordetecting an amount of force applied to the brake operating element; afluid pressure-generating unit capable of generating a fluid pressureindependently from an operation of said brake operating element, apressure-regulating unit interposed between said fluidpressure-generating unit and a wheel brake for regulating an outputfluid pressure of said fluid pressure-generating unit and applying theregulated fluid pressure to said wheel brake, and a control unit forcontrolling the operation of said pressure-regulating unit on the basisof a signal from said operating amount detector, saidpressure-regulating unit being disposed on the rear side of said enginebody, wherein as seen in a top plan view thereof, said fluidpressure-generating unit is disposed between and supported by said leftand right seat rails.
 2. The motorcycle as set forth in claim 1, whereinsaid fluid pressure-generating unit is flexibly supported, through aflexibly resilient member, by a first support member which is attachedto one of said seat rails, and by a crossmember which connects both saidseat rails to each other.
 3. The motorcycle as set forth in claim 2,wherein a second support member is firmly attached to said crossmember,and an attaching member, fixed to said fluid pressure-generating unit,is supported by said second support member through a flexibly resilientmember.
 4. The motorcycle as set forth in claim 1, further comprising: aswing arm which is pivotally attached to said body frame and issupported for reciprocal movement thereon; a rear wheel which isrotatably attached to said swing arm; a link mechanism provided betweensaid swing arm and said body frame, said link mechanism comprising alink member; a shock absorber extending between said swing arm and saidlink member; and a sub-tank for conditioning a damping force of saidshock absorber, said sub-tank disposed on the rear side of said fluidpressure-generating unit and supported by said seat rail.
 5. Themotorcycle as set forth in claim 2, further comprising: a swing armwhich is pivotally attached to said body frame and is supported forreciprocal movement thereon; a rear wheel which is rotatably attached tosaid swing arm; a link mechanism provided between said swing arm andsaid body frame, said link mechanism comprising a link member; a shockabsorber extending between said swing arm and said link member; and asub-tank for conditioning a damping force of said shock absorber, saidsub-tank disposed on the rear side of said fluid pressure-generatingunit and supported by said seat rail.
 6. The motorcycle as set forth inclaim 3, further comprising: a swing arm which is pivotally attached tosaid body frame and is supported for reciprocal movement thereon; a rearwheel which is rotatably attached to said swing arm; a link mechanismprovided between said swing arm and said body frame, said link mechanismcomprising a link member; a shock absorber extending between said swingarm and said link member; and a sub-tank for conditioning a dampingforce of said shock absorber, said sub-tank disposed on the rear side ofsaid fluid pressure-generating unit and supported by said seat rail. 7.The motorcycle as set forth in claim 4, wherein a sub-tank supportmember for supporting said sub-tank is fixed to said seat rail byco-fastening together with a pillion step.
 8. A motorcycle comprising: abody frame comprising left and right seat rails which are spaced apartfrom one another and provided to support a seat thereon; an enginemounted on said body frame, said engine comprising an engine body; awheel brake; a manually operable brake operating element which isfluidly connected to said wheel brake; and a brake-by wire systemcomprising: an operation amount detector for detecting an amount offorce applied to the brake operating element; a fluidpressure-generating unit capable of generating a fluid pressureindependently from an operation of said brake operating element, apressure-regulating unit interposed between said fluidpressure-generating unit and a wheel brake for regulating an outputfluid pressure of said fluid pressure-generating unit and applying theregulated fluid pressure to said wheel brake, and a control unit forcontrolling the operation of said pressure-regulating unit on the basisof a signal from said operating amount detector, saidpressure-regulating unit being disposed on the rear side of said enginebody, wherein as seen in a top plan view thereof, said fluidpressure-generating unit is disposed between and supported by said leftand right seat rails; wherein said fluid pressure-generating unit isflexibly supported, through a flexibly resilient member, by a firstsupport member which is attached to one of said seat rails, and by acrossmember which extends between and connects both said seat rails; andwherein a second support member is firmly attached to said crossmember,and an attaching member, fixed to said fluid pressure-generating unit,is supported by said second support member through a flexibly resilientmember.
 9. The motorcycle as set forth in claim 8, further comprising: aswing arm which is pivotally attached to said body frame and issupported for reciprocal movement thereon; a rear wheel which isrotatably attached to said swing arm; a link mechanism provided betweensaid swing arm and said body frame, said link mechanism comprising alink member; a shock absorber extending between said swing arm and saidlink member; and a sub-tank for conditioning a damping force of saidshock absorber, said sub-tank disposed on the rear side of said fluidpressure-generating unit and supported by said seat rail.
 10. Themotorcycle as set forth in claim 9, wherein a sub-tank support memberfor supporting said sub-tank is fixed to said seat rail by co-fasteningtogether with a pillion step.
 11. A motorcycle comprising: a body framecomprising left and right seat rails which are spaced apart from oneanother and provided to support a seat thereon; an engine mounted onsaid body frame, said engine comprising an engine body; a wheel brake; amanually operable brake operating element which is fluidly connected tosaid wheel brake; a swing arm which is pivotally attached to said bodyframe and is supported for reciprocal movement thereon; a rear wheelwhich is rotatably attached to said swing arm; a link mechanism providedbetween said swing arm and said body frame, said link mechanismcomprising a link member; a shock absorber extending between said swingarm and said link member; and a sub-tank for conditioning a dampingforce of said shock absorber, said sub-tank disposed on the rear side ofsaid fluid pressure-generating unit and supported by said seat rail; anda brake-by wire system comprising: an operation amount detector fordetecting an amount of force applied to the brake operating element; afluid pressure-generating unit capable of generating a fluid pressureindependently from an operation of said brake operating element, apressure-regulating unit interposed between said fluidpressure-generating unit and a wheel brake for regulating an outputfluid pressure of said fluid pressure-generating unit and applying theregulated fluid pressure to said wheel brake, and a control unit forcontrolling the operation of said pressure-regulating unit on the basisof a signal from said operating amount detector, saidpressure-regulating unit being disposed on the rear side of said enginebody, wherein as seen in a top plan view thereof, said fluidpressure-generating unit is disposed between and supported by said leftand right seat rails.
 12. The motorcycle as set forth in claim 11,wherein said fluid pressure-generating unit is flexibly supported,through a flexibly resilient member, by a first support member which isattached to one of said seat rails, and by a crossmember which connectsboth said seat rails to each other.
 13. The motorcycle as set forth inclaim 12, wherein a second support member is firmly attached to saidcrossmember, and an attaching member, fixed to said fluidpressure-generating unit, is supported by said second support memberthrough a flexibly resilient member.
 14. The motorcycle as set forth inclaim 11, wherein a sub-tank support member for supporting said sub-tankis fixed to said seat rail by co-fastening together with a pillion step.